What are Weed Grasses?

Weed (or course) grasses are types of grass that appear in your lawn that are a different colour and texture to the rest. In some cases, these can be an unattractive, and unwanted addition that makes your lawn appear patchy.

What are the Causes?

There are several possible causes for course grasses to appear:

  • Seeds could be introduced by birds, in imported soils, or in newly laid turf.
  • Thanks to the hardy and adaptable nature of these grasses, they can also appear when your lawn is stressed due to compaction, drought, underfeeding, or excessive mowing.
  • During the winter months when the fine grasses are dormant, coarse grasses continue to develop.
  • Other elements to consider are that soil is lacking in nutrition or minerals or soil pH is too high or low and on bare soil the weed grasses replace the desired grasses.

Types of Grasses

Poa Annua (AMG)

Poa annua (annual meadow grass) is a small native grass that seeds freely, even when turf is mown very close. Although it is usually an annual, there are strains which tend to be biannual or even perennial. It’s an amazing grass which is genetically unstable allowing it to adapt to most environmental conditions, making it difficult to eradicate it. Most turf contains a small element of this. It is typically visible due to flowering at a very low level within the sward. It looks worst during May to July. AMG will remain in turf, but by maintaining good growing conditions, the effect will be minimized.

Yorkshire Fog

Yorkshire Fog is a wild grass found in fields and verges; it is quite ubiquitous. Unlike AMG it is rarely found in turf but is quite adapt at entering a sward. It is a pale green colour with wide hoary blades which spreads into a mat within the sward.


To avoid pests, diseases, and weeds in your lawn it is good practice to follow our annual lawncare plan. For immediate action to eradicate weed grasses try the following steps:

  • There are no chemical controls without killing off your desirable grasses too. There are some products on the market, however, that if they make contact with the desired grasses, it will kill them, therefore remove the weed grasses by hand. This can be done with a hand fork, fill hole with soil, then reseed or turf the area.
  • Rake the lawn lightly to lift up the patches of weed grass before mowing, this will allow a better cut and aid weed grass removal.
  • Mow regularly with a sharp blade as fine grasses are better adapted to being cut, whilst weed grasses are weakened by continuous mowing. Mow at 50mm, this will help shade out the AMG.
  • Verticut and scarify regularly
  • Aerate the areas regularly
  • Check pH and keep areas well fed etc.
  • Making the conditions as suitable for grass growth as possible; remove tree branches etc.

What else might be the problem?

It may not be weed grasses that are causing your lawn problems. Be on the look out for these common issues and click on the links to find out more:

Download our advice leaflet here.